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SrOERS  AGElCtrLTOEAL  ElPERDfflNT  STATION,     s 

.        43 

CONNECTICUT 

Agricultural  Experiment  Station 

NE\V   HAVEN,  CONN. 


BULLETIN  215  DECEMBER,  1919 


ECONOMY  IN  FEEDING  THE  FAMILY 


THE  FOOD  VALUE  OF  MILK 

By  Edna  L.    Ferry 


CONTENTS 

Page 
Introduction 3 

Constitution  of  Proteins 4 

Tiie  Proteins  of  Milk 7 

The  Vitamines  of  Milk 2i 

The  Sugar  of  Milk 28 

The  Mineral  Matters  of  Milk 28 

The  Cost  and  Economy  of  Milk 28 

Summary 30 

The  Bulletins  of  this  Station  are  mailed  free  to  citizens  of  Connecticut  who 
apply  for  them,  and  to  others  as  far  as  the  editions  permit. 


CONNECTICUT  AGRICULTURAL  EXPERIMENT  STATION 

OFFICERS  AND  STAFF 
December,  1919. 


BOARD  OF  CONTROL. 
His  Excellency,  Marcus  H.  Holcomb,  ex-officio.  President. 

James  H.  Webb,  Vice  President Hamden 

George  A.  Hopson,  Secretary New  Haven 

E.  H.  Jenkins,  Director  and  Treasurer New  Haven 

Joseph  W.  Alsop Avon 

Charles  R.  Treat Orange 

Elijah  Rogers  Southington 

William  H.  Hall South  Willington 


Administration. 


Chemistry. 
Analytical  Laboratory. 


Protein  Research. 
Botany. 


Entomology. 

Forestry. 

Plant  Breeding. 
Vegetable   Growing. 


STAFF. 

E.  H.  Jenkins,  Ph.D.,  Director  and  Treasurer. 

Miss  V.  E.  Cole,  Librarian  and  Stenographer. 

Miss  L.  M.  Brautlecht,    Bookkeeper    and    Stenographer. 

William  Veitch,  In  charge  of  Buildings  and  Grounds. 

E.  Monroe  Bailey,  Ph.D.,  Chemist  in  charge. 

R.  E.  Andrew,  M.A.  ^ 

C.  E.  Shepard,  I  Assistant  Chemists. 

H.  D.  Edmond,   B.S.  j 

Frank  Sheldon,  Laboratory  Assistant. 

V.  L.  Churchill,  Sampling  Agent. 

Miss  Alxa  H.  Moss,  Clerk. 

T.  B.  Osborne,  Ph.D.,  D.Sc,  Chemist  in  Charge. 

G.  P.  Clinton,  Sc.D.,  Botanist. 

E.  M.  Stoddard,.  B.S.,  Assistant  Botanist. 

Miss  Florence  A.  McCormick,  Ph.D.,  Scientific  Assistant. 

G.  E.  Graham,  General  Assistant. 

Mrs.  W.  W.  Kelsey,  Secretary. 

W.  E.  Britton,  Ph.D.,  Entomologist;  State  Entomologist. 

B.  H.  Walden,  B.Agr.,  Phillip  Carman,  Ph.D. 

M.  P.  Zappe,  B.S.,  I.  W.  Davis,  B.Sc,  K.  F.  Chamberlain, 

Assistants. 

Miss  Gladys  M.  Finley,  Stenographer. 

Walter  O.  Filley,  Forester,  also  State  Forester 

and  State  Forest  Fire  Warden. 
A.  E.  Moss,  M.F.,  Assistant  State  and  Station  Forester. 
H.  W.  HicoCK,  M.F.,  Assistant. 
Miss  E.  L.  Avery,  Stenographer. 

Donald  F.  Jones,  S.D.,  Plant  Breeder. 

C.  D.  HuBBELL,  Assistant. 

W.  C.  Pelton,  B.S. 


THE  FOOD  VALUE  OF  MILK 

At  the  annual  meeting  of  the  Connecticut  Dairymen's  Asso- 
ciation in  January,  1919,  Miss  Edna  L.  Ferry  of  this  Station 
gave  an  address  with  the  above  title. 

"At  the  conclusion  of  Miss  Ferry's  address  it  was  voted  to  ask  the 
Experiment  Station  to  prepare  a  bulletin  on  the  food  value  of  milk 
which  could  be  distributed  among  consumers." 

In  response  to  the  request  this  bulletin  has  been  prepared, 
which  is  largely  a  transcript  of  Miss  Ferry's  paper.  Her  untimely 
death  has  put  on  others  the  work  of  editing  it  which  has  consisted 
chiefly  in  slight  changes  in  form  and  arrangement. 

Introduction. 

Milk  is  the  only  food  that  supplies  all  of  the  food  elements 
which  the  new-born  animal  must  have  in  order  to  live  and  grow. 

Among  wandering  Indian  tribes  the  child  whose  mother  fails 
to  nurse  it  is  doomed  to  die  because  no  other  milk  can  be  had. 

In  countries  where  milch  animals  are  scarce,  as  in  Japan  and 
China,  mothers  from  necessity,  if  not  from  choice,  nurse  their 
children  for  relatively  long  periods,  sometimes  for  two  and  even 
three  years. 

In  countries  where  dairy  cattle  are  abundant  the  cow  is  the 
foster  mother  of  a  large  part  of  the  infant  population  which  for 
one  reason  or  another  does  not  have  its  mother's  milk. 

The  world  has  had  no  more  pitiful  tragedies  in  the  present  war 
than  the  starving  to  death — or  to  life-long  inefficiency — of  a  large 
infant  population. 

Hoover,  who  had  the  best  chance  to  observe  and  who  is  given 
to  sober  statement  without  exaggeration,  says : 

"One  of  the  first  acts  of  the  Germans  was  to  denude  the  people  of 
Belgium  to  a  very  large  extent  and  the  north  of  France  almost  wholly 
of  their  cattle.  In  consequence  it  has  been  necessary  to  maintain  a 
stream  of  condensed  milk  for  the  whole  of  the  last  four  years. 

"The  European  races  are  absolutely  dependent  for  the  rearing  of  their 
young  on  these  cattle.  There  is  no  cruelty  to  a  population  greater  than 
to  rob  them  of  their  dairy  stock." 

The  need  of  milk  is  not  limited  to  the  first  year  of  life.  When 
the  child  is  able  to  enlarge  its  diet  and  take  solid  food,  milk  is 


4  CONNECTICUT   EXPERIMENT    STATION    BULLETIN    215. 

an  indispensable  adjunct.  Of  the  27  brands  of  "infant  foods" 
in  market,  which  were  examined  by  this  Station  (Report  191 5, 
p.  324),  16  claim  to  contain  milk  and  the  directions  for  the  use 
of  9  others  prescribe  mixture  with  milk. 

All  through  childhood  and  youth  bread  and  milk  and  cereal 
and  milk  are  recognized  as    "growing  foods." 

Milk,  too,  is  the  most  commonly  prescribed  food  for  adults  in 
severe  illness  and  a  resource  in  time  of  sudden  exhaustion. 

It  is  hardly  too  much  to  say  that  public  health,  content  and 
civilization  follow  the  cow. 

The  work  of  Dr.  Osborne  at  this  Station  has  largely  con- 
tributed to  the  discovery  of  the  reasons  for  this  unique  value 
of  milk  which  are  leading  to  a  greater  appreciation  and  more 
rational  use  of  it.  This  work  has  been  in  a  way  incidental  to  a 
general  study  of  the  character  and  function  of  proteins  and  of 
the  laws  of  nutrition.  The  investigations  on  the  chemistry  of  the 
proteins  have  been  carried  on  for  many  years  by  Dr.  Osborne 
and  in  the  nutrition  studies  which  followed  he  has  had  the 
valuable  cooperation  of  Dr.  Lafayette  B.  Mendel  of  Yale 
University. 

Constitution  of  Proteins. 

The  foundation  of  our  new  knowledge  regarding  milk  was 
laid  by  finding  out  and  setting  forth  the  composition  and  struc- 
ture of  a  large  number  of  different  proteins,  which  are  the  flesh- 
growing  materials  of  the  body  and  an  indispensable  part  of  all 
the  vital  body  fluids.  This  work  showed  for  the  first  time  their 
great  variety  and  the  fact  that  a  nearly  identical  percentage 
composition  of  their  elements  (nitrogen,  carbon,  oxygen,  hydro- 
gen, and  sometimes  sulphur  and  phosphorus)  went  along  with 
wide  differences  in  structure  and  in  physical  and  chemical 
properties ;  and  that  in  the  same  food  material,  whether  animal 
or  vegetable,  two  or  more  proteins  of  quite  different  quality 
were  usually  found  together. 

Dr.  Osborne's  work,  with  that  of  others,  showed  that  a  protein 
was  no  such  simple  thing  as  salt  or  sugar,  but  was  made  up  of 
about  eighteen  different  complexes,  knots  of  nitrogen-containing 
groups  called  amino-acids,  each  of  them  a  complicated  structure 
in  itself. 


CONSTITUTION   OF  PROTEINS. 


The  following  table  gives  the  names  of  these  amino-acids, 
the  approximate  percentage  of  each  in  several  of  the  common 
proteins  and  shows  the  striking  differences  in  their  amount. 

Comparative  composition  of  proteins. 


AMINO-ACIDS 


Glycocoll    

Alanine    

Valine     

Leucine    

Proline     

Phenylalanine     .... 

Aspartic  acid   

Glutaminic   acid    . . 

Serine    

Tyrosine    

Cystine    

Histidine    

Arginine     

Lysine    

Tryptophane,   about 
Ammonia    


ZEIN 

(maize) 


per  cent. 

o.oo 

13-39 
1.88 

19-55 
9.04 

6.55 

1.71 

26.17 

1.02 

3-55 
? 

0.82 

1-55 
0.00 
0.00 
3-64 


GLIADIN 

(wheat) 


per  cent. 

0.00 
2.00 

3-34 
6.62 

13.22 
2.35 
0.58 

43.66 
0.13 
1.50 
0.45 
1.49 
3.16 
? 

1. 00 

5-22 


casein 
(milk) 


per  cent. 
0.00 

1.50 

7.20 

9-35 
6.70 
3-20 
1-39 
15-55 
0.50 

4-50 

? 

2.50 
3.81 
7.61 
1.50 
1.61 


lactal- 

BUMIN 

(milk) 


per  cent. 

0.00 
2.50 
0.90 

19.40 
4.00 
2.40 
1. 00 

10.10 

? 

2.20 

? 

1-53 
3.01 
8.10 

+ 
1.32 


EDESTIN 

(hemp.- 
seed) 


per  cent. 

3-80 
3.60 
6.20 

14.50 

4.10 
3-09 
4-SO 

18.74 
0.33 
2.13 
1. 00 
2.19 

14.17 
i-6s 


88.87 


\.72 


66.92 


56.46 


82.2? 


In  view  of  these  great  differences  of  structure  and  composi- 
tion of  proteins,  the  question  arose :  have  they  nevertheless 
about  the  same  food  value  as  has  been  assumed,  or  have  they  not  ? 
If  they  have  not,  the  principles  on  which  our  whole  art  of  cattle 
feeding  is  founded  has  lost  a  large  part  of  its  foundation. 

Clearly,  the  only  w^ay  to  settle  the  question  was  to  study  the 
feeding  effect  of  each  protein  by  itself  on  both  growth, 
maintenance  and  production. 

Before  the  work  here  was  begun,  all  experimenters  who  en- 
deavored to  feed  animals  on  diets  composed  of  pure  nutrients 
failed.  Both  mature  and  young  animals  promptly  declined  in 
weight  on  such  diets.  To-day  we  have  such  an  understanding 
of  the  influence  of  food  on  growth  that  merely  by  changing  a 
single  constituent  of  the  diet  we  can  stop  the  growth  of  a  young 
animal  at  any  stage  of  development,  maintain  it  for  many  months 
in  perfect  health,  but  without  growth,  and  later  cause  it  to  grow 


6  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    21 5. 

again  at  a  normal  rate  to  full  maturity  and  reproduce.  It  is 
due  to  the  use  of  milk  in  the  earlier  attempts  in  feeding  animals 
experimentally  that  we  owe  our  success  in  developing  methods 
of  feeding  which  have  opened  up  entirely  new  fields  for 
investigation. 

Our  first  attempts  to  make  an  animal  grow  on  a  mixture  of 
pure  protein,  fat,  carbohydrate  and  inorganic  salts  were  no  more 
successful  than  those  of  our  predecessors,  but  we  soon  found 
that  animals  which  failed  to  thrive  on  our  artificial  diets  could 
be  restored  promptly  to  excellent  condition  by  giving  them  a 
mixture  of  dried  milk,  starch  and  lard,  and  that  control  animals 
fed  on  a  similar  diet  from  weaning  grew  normally  to  full  maturity 
and  reproduced.  Although  the  artificial  diets  were  almost  exactly 
like  the  milk  diets,  in  respect  to  the  kind  and  proportion  of  the 
then  known  nutrients,  the  milk  diet  was  entirely  adequate  as  a 
food,  whereas  the  artificial  diet  was  wholly  inadequate.  Wherein 
this  profound  difference  lay  was  a  mystery.  By  a  process  of 
elimination  we  were  forced  to  the  conclusion  that  the  water- 
soluble  portion  of  the  milk  contained  something  which  was 
essential  for  life,  and  later  that  the  fat  component  contained 
something  which  was  indispensable  for  long-continued  growth. 
This  discovery  that  milk  contains  two  hitherto  unsuspected 
substances,  now  known  as  the  water-soluble  and  fat-soluble 
vitamines,  which  will  be  referred  to  later,  made  it  possible  for 
us  to  become  pioneers  in  the  study  of  various  problems  relating 
to  growth  and  maintenance.  The  field  of  study  thus  opened  has 
been  entered  by  numerous  investigators  here  and  abroad  with 
results  of  far-reaching  importance. 

The  experiments  here  to  be  described  were  made  with  albino 
rats  because  these  small  animals  are  omnivorous  and  can  be  fed 
with  such  quantities  of  the  experimental  rations  as  we  are  able 
to  prepare  in  the  laboratory  in  a  state  of  purity.  To  insure 
perfect  accuracy  it  is  necessary  that  these  rations  shall  consist 
of  ingredients  which  are  chemically  pure  and  to  prepare  such 
rations  in  quantity  is  very  laborious  and  costly.  The  results  of^ 
these  experiments  can  be  accepted  as  giving  evidence  of  the 
true  food  value  of  milk  because  they  are  in  harmony  with  our 
experience  in  feeding  not  only  ourselves  but  also  farm  animals. 

The  question  may  be  asked — Are  the  results  of  experiments  in 


CONSTITUTION  OF  PROTEINS.  7 

feeding  rats,  or  other  of  the  lower  animals,  applicable  to  human 
beings  ? 

While  the  foods  suited  to  different  species  of  animals  may 
differ  widely  in  their  appearance  and  physical  properties,  the 
digestible  nutrients  contained  in  them  are  very  much  alike  in  their 
chemical  characters,  so  that  by  the  processes  of  digestion  quite 
similar  products  result  from  apparently  very  different  kinds  of 
food.  Such  differences  as  exist  are  rather  in  proportion  than  in 
kind.  Furthermore,  the  tissues  of  the  different  types  of  animals 
are  chemically  even  more  alike  than  their  foods  and,  consequently, 
their  nutritive  requirements  are  in  principle  much  more  nearly 
the  same  than  those  unfamiliar  with  the  chemistry  of  nutrition 
would  suppose. 

The  conditions  in  feeding  farm  animals  are  necessarily  so 
complex  that  it  is  generally  impossible  to  recognize  the  influence 
of  any  individual  constituent  of  the  ration.  In  our  experiments 
with  rats,  on  the  contrary,  the  conditions  have  been  so  simplified 
that  definite  conclusions  can  be  drawn  regarding  the  role  of  each 
factor  involved.  Thus,  if  two  series  of  animals  are  fed  on  mix- 
tures of  protein,  fat,  carbohydrate  and  inorganic  salts,  which  are 
identical  except  for  the  kind  of  protein  used,  and  one  series  grows 
normally  whereas  the  other  fails  to  grow  at  all,  it  is  obvious  that 
the  protein  alone  was  the  determining  element  in  the  food.  By 
means  of  large  numbers  of  such  experiments  extending  over  a 
period  of  several  years,  we  have  fixed  the  nutritive  values  of 
many  proteins,  several  fats,  the  various  inorganic  salts  and  also 
have  studied  a  number  of  combinations  of  natural  food  products 
both  of  animal  and  vegetable  origin  which  are  extensively  used 
in  the  daily  rations  of  man  or  domestic  animals. 

The  Proteins  of  Milk. 
Previous  to  1912  a  discussion  of  the  nutritive  value  of  any 
food  stuff  would  have  been  confined  to  a  consideration  of  the 
total  quantities  of  protein,  fat,  carbohydrate  and  salts  which  it 
contained  and  its  value  as  a  source  of  energy.  As  a  result  of 
work  which  has  been  done  at  this  Station,  and  later  in  other 
laboratories,  the  field  for  discussion  has  become  much  broader, 
for  it  has  been  demonstrated  that  the  quality  of  the  protein 
present  in  any  food  is  of  even  more  importance  than  the  quantity, 


8  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    215. 

and  a  realization  of  the  essential  role  which  the  so-called  vita- 
mines  play  in  normal  nutrition  has  raised  many  more  problems. 

Milk  contains  several  different  proteins,  but  there  are  only 
two  which  occur  in  notable  quantity,  and  these  are  casein,  the 
protein  found  in  cheese,  and  lactalbumin,  the  principal  protein 
of  whey.  These  two  proteins  differ  not  only  in  their  chemical 
structure,  but  also  in  their  nutritive  value.  Both  suffice  to  pro- 
mote the  normal  growth  of  young  rats,  but  lactalbumin  is  some- 
what more  efficient  for  growth  than  is  casein,  for  in  comparable 
periods  of  time  a  given  quantity  of  lactalbumin  will  enable  an 
animal  to  gain  about  33  per  cent,  more  in  weight  than  the  same 
amount  of  casein. 

This  is  instructive  from  a  practical  standpoint  for  it  demon- 
strates that  the  whey,  obtained  as  a  side  product  from  the  manu- 
facture of  cheese,  contains  one  of  the  most  valuable  food  proteins 
known  and  should  not  be  wasted.  Casein,  which  forms  about 
80  per  cent,  of  the  milk  proteins,  is  more  easily  digested  than 
any  other  protein  known  and  behaves  in  the  digestive  tract  very 
much  like  a  predigested  protein.  This  property  makes  it 
especially  desirable  as  a  food  for  infants  or  persons  with  weak 
digestions. 

For  centuries  people  have  been  accustomed  to  use  foods  of 
animal  origin  with  bread  and  other  cereal  products  which  form 
so  large  a  proportion  of  the  average  dietary.  Bread  and  milk, 
eggs  on  toast,  meat  sandwiches  and  the  use  of  milk  on  breakfast 
cereals  are  just  a  few  illustrations  of  this  custom.  If  any  one 
who  was  enjoying  a  meal  of  any  of  these  mixtures  were  asked 
why  he  chose  the  combination  of  the  animal  with  the  vegetable 
product  instead  of  eating  either  one  alone,  he  would  probably 
say  that  "it  tasted  good."  or  "it  satisfied  his  appetite  better 
that  way,"  or  something  else  equally  indefinite.  It  is  only 
recently,  while  engaged  in  investigating  the  nutritive  value  of 
wheat  flour,  that  we  discovered  how  well  the  proteins  of  milk, 
eggs  and  meat  supplement  the  deficiencies  of  the  wheat  proteins. 
We  now  have  a  truly  scientific  reason  for  this  universal  dietary 
practice. 

If  an  animal  is  fed  on  wheat  flour  as  the  sole  source  of  protein 
in  an  otherwise  adequate  ration,  it  will  grow  very  slowly,  if  at 
all,  even  when  relatively  large  amounts  of  the  proteins  are  eaten. 
If,  however,  one-third  of  the  wheat  protein  is  replaced  by  an 


THE  PROTEINS  OF  MILK. 


equivalent  quantity  of  protein  in  the  form  of  milk,  eggs,  or  meat, 
the  animal  will  grow  at  a  practically  normal  rate. 


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To  illustrate  this  as  well  as  the  results  of  our  other  experi- 
ments with  various  diets  of  known  composition,  in  a  condensed 
form,    we   have    employed    charts    giving    the    curves    of    body 


lb  CONNECTICUT   EXPERIMENT    STATION    BULLETIN    215. 

weight  during  the  time  of  feeding.  In  reading  these  charts  the 
squares  running  horizontally  represent  time  of  feeding  expressed 
in  days,  running  vertically  the  weight  of  the  animal  in  grams 
(i  gram  equals  about  Vao  of  an  ounce).  The  heavy  black  lines 
show  the  rate  at  which  the  animal  gained  weight;  the  more 
nearly  vertical  these  lines  the  more  rapid  the  growth. 

Chart  I  gives  a  graphic  representation  of  the  curves  of  growth 
of  a  number  of  rats  which  have  been  fed  in  these  ways,  and 
Figure  i  gives  the  photographs  of  two  of  these  animals. 


Figure  i 

•  Rat  ^2']']  was  fed  on  a  diet  in  which  gliadin  from  wheat  flour  furnished 
the  protein.  On  this  food  he  gained  only  10  grams  in  ten  weeks.  Rat 
5314  was  fed  on  a  mixture  of  wheat  flo^ir  and  milk.  On  this  food  he 
gained  160  grams  in  nine  weeks.  This  illustrates  the  importance  of 
combining  milk  with  the  cereals  instead  of  feeding  the  cereals  alone. 

All  of  the  animals  shown  in  this  chart  were  of  the  same  size 
and  age,  and  were  growing  vigorously  when  put  on  the  experi- 
mental diets.  The  differences  in  size  at  the  end  of  each  experi- 
ment are  due  solely  to  the  protein  of  the  diet.  In  this  series  of 
experiments  the  percentage  of  protein  and  nutritive  ratio  of  the 
mixtures  were  practically  identical,  the  foods  differing  only  in 


THE  PROTEINS  OF  MILK.  I  I 

the  kind  of  protein.  The  animals  in  the  group  labelled  "flour" 
received  all  of  their  protein  from  wheat  flour,  those  in  the  groups 
labelled  "flour  +  milk,"  "flour  +  egg,"  and  "flour -|- meat" 
received  a  diet  whose  concentration  of  protein  was  the  same  as 
that  of  the  "flour"  group,  but  one^third  of  the  protein  was 
furnished  by  milk,  egg,  or  meat  respectively,  the  remaining  two- 
thirds  being  furnished  by  flour.  It  is  obvious  that  relatively 
small  quantities  of  these  animal  proteins  greatly  improved  the 
value  of  the  food  for  growth.  The  value  of  these  animal  products 
lies  in  the  fact  that  they  are  chemically  so  constituted  as  to  , 
supplement  the  chemical  deficiencies  of  the  flour  proteins.  To 
those  who  are  unfamiliar  with  the  chemistry  of  proteins  this 
may  seem  mysterious  and  confusing,  hence  a  few  words  of 
explanation  are  necessary. 

By  digestion  the  proteins  are  broken  up  into  the  amino-acids 
already  mentioned  on  page  5,  which  are  then  used  in  con- 
structing the  new  proteins  of  the  tissues  of  the  growing  animal. 
Unless  the  food  protein  furnishes  a  sufficient  amount  of  each 
of  these  amino-acids  which  are  needed  to  make  the  tissues 
required  for  normal  growth  the  animal  grows  correspondingly 
slower  than  it  would  if  more  of  the  needed  amino-acid  were 
available. 

Wheat  flour  contains  two  proteins,  one  of  which,  called  gliadin, 
yields  only  a  very  small  amount  of  the  amino-acid  called  lysine. 
The  effect  of  a  limited  supply  of  lysine  on  growth  is  illustrated 
by  rats  5277  and  5265,  whose  curves  of  body  weight  are  shown 
in  Chart  i.  These  were  fed  on  a  diet  in  which  all  of  the  protein 
was  furnished  by  gliadin.  They  have  been  maintained  in  good 
health,  but  have  gained  only  about  10  grams. 

The  rats  on  the  "flour"  diets  grew  somewhat  more  than  those 
on  the  gliadin  food  because  flour  contains  another  protein  which 
yields  more  lysine  than  does  gliadin  and  hence  supplements  to 
some  extent  this  deficiency  of  the  gliadin.  However,  the  amount 
of  lysine  thus  supplied  was  too  little  to  promote  normal  growth. 
In  this  connection  it  is  interesting  to  note  how  perfectly  a  young 
animal  can  be  maintained  in  health,  but  without  growing  even 
for  a  very  long  time  when  its  diet  is  adequate  in  respect  to 
everything  except  the  chemical  constitution  of  its  food  protein. 
Such  animals  can  be  thus  kept  as  infants  for  indefinite  periods. 


12  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    215. 

Chart  II  shows  how  Httle  growth  was  made  during  nine  months 
on  a  diet  in  which  ghadin  from  wheat  flour  furnished  all  the 
protein.  At  the  end  of  these  nine  months  the  rat  was  given  a 
similar  diet  containing  enough  dried  milk  to  replace  the  gliadin, 


Figure  2 

Figure  2  shows  the  contrast  between  feeding  a  good  or  a  bad  protein 
to  a  young  rat.  The  two  tipper  rats  are  five  months  old  and  have  been 
fed  on  diets  exactly  alike  except  the  one  at  the  top  had  casein  from  milk 
on  which  it  grew  normally,  and  the  one  in  the  middle  had  gliadin  from 
wheat  flour  on  which  it  could  not  grow  at  all,  so  that  when  it  was  five 
months  old  it  weighed  exactly  the  same  as  the  rat  at  the  bottom  which 
was  only  one  month  old. 


and  in  two  weeks  on  that  food  it  gained  as  much  in  body  weight 
as  it  had  during  the  preceding  nine  months.  It  continued  to 
grow  normally  on  the  milk  diet  to  full  adult  size;  a  striking 
illustration  of  the  value  of  milk  proteins  for  growth.    If,  instead 


THE  PROTEINS  OF  MILK. 


13 


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14  CONNECTICUT   EXPERIMENT   STATION   BULLETIN    21 5. 


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THE  PROTEINS  OF  MILK.  1 5 

Chart  III  shows  the  weight  curves  of  several  rats  whose 
growth  was  alternately  stimulated  or  checked  by  the  addition  to 
a  gliadin  diet  of  very  small  quantities  of  lysine  or  by  its  removal. 

In  every  day  practice,  however,  it  is  impossible  to  feed  lysine, 
as  such,  and  therefore  the  problem  resolves  itself  into  finding 
available  proteins  which  are  sufficiently  rich  in  lysine  to  be 
capable  of  supplementing  this  deficiency  of  the  flour  proteins. 
The  two  foods  which  thus  far  have  proved  to  be  the  most  efficient 
supplements  to  flour  are  milk  and  eggs ;  either  of  these  is  some- 
what better  than  meat.  Thus  under  similar  conditions  of  feeding 
when  the  food  contains  two  parts  of  flour  proteins  to  one  part  of 
meat  protein  rats  gain  about  three  times  as  much  per  unit  of 
protein  eaten  as  when  flour  furnishes  all  the  protein,  and  nearly 
four  times  as  much  when  milk  or  eggs  are  used  as  supplements. 

The  same  is  true  for  corn  supplements.  Zein,  the  principal 
protein  of  corn,  lacks  two  essential  amino-acids,  tryptophane  and 
lysine,  hence  when  zein  furnishes  all  of  the  protein  of  the  diet, 
the  animal  loses  weight-  rapidly  and  dies  almost  as  soon  as  if  no 
food  were  eaten.  When  a  small  quantity  of  one  of  these  missing 
amino-acids,  tryptophane,  is  added  to  the  zein  diet,  the  animal 
maintains  its  weight  and  lives  for  a  long  time  but  does  not  grow. 
If  in  addition  to  tryptophane,  lysine  also  is  added,  the  animal 
grows. 


i6 


CONNECTICUT   EXPERIMENT    STATION   BULLETIN    215. 


Chart  IV  shows  the  important  part  played 
by  amino-acids  in  nutrition.  Zein,  which  forms 
about  one-half  the  protein  of  corn  meal,  lacks 
two  of  these,  known  as  tryptophane  and  lysine. 
Unless  tryptophane  is  added  to  a  diet  contain- 
ing zein  as  its  sole  source  of  protein,  life  can- 
not long  be  maintained.  Unless  lysine  is  also 
added,  growth  is  impossible.  The  proteins  of 
milk  contain  an  abundance  of  both  of  these 
amino-acids. 


Chart  IV  shows  the  curves  of  body 
weight  of  rats  receiving  zein  alone  as 
well  as  zein  in  combination  with  trypto- 
phane or  with  tryptophane  and  lysine. 
Note  that  the  body  weight  of  one  of 
these  rats  remained  constant  for  six 
months  when  the  diet  contained  zein  and 
tryptophane.  When  small  amounts  of 
both  lysine  and  tryptophane  were  added 
to  the  zein  food  the  rat  grew. 


3  SWll/£)^. 


THE  PROTEINS  OF  MILK. 


17 


Figure  3  shows  in  a  striking  manner  how  essential  it  is  to 
supply  the  young  animal  with  protein  which  furnishes  sufficient 
lysine.  The  lower  picture  is  that  of  a  young  rat  which  lived  for 
seven  months  in  perfect  health  on  a  food  containing  zein  -)-  trypto- 
phane as  its  sole  protein.  During  all  of  this  time  it  failed  to 
grow  and  weighed  only  70  grams.     It  did  not  even  show  signs 


Figure   3. 

The  lower  photograph  is  that  of  a  rat  which  has  been  fed  for  seven 
months  on  a  diet  containing  zein  (one  of  the  proteins  from  corn)  +  a 
small  amount  of  amino-acid  tryptophane.  On  this  diet  the  rat  could  live 
but  could  not  grow.  The  upper  photograph  is  one  of  the  same  animal 
taken  a  few  months  later,  after  casein  from  milk  had  replaced  the  zein 
and  tryptophane. 


of  maturing  for,  as  you  can  see,  it  looks  exactly  like  a  recently 
weaned  rat ;  it  has  remained  a  baby.  At  the  end  of  seven  months 
casein  was  used  to  replace  the  zein  -|-  tryptophane.  No  other 
change  was  made  in  the  diet.  During  the  next  three  months  it 
grew  at  the  normal  rate  to  230  grams,  and  as  the  upper  picture 
shows,  became  a  fine,  vigorous  animal. 


CONNECTICUT    EXPERIMENT    STATION   BULLETIN    215. 


What  this  means  might  be  illustrated  in  this  way.  For  about 
one-fifth  of  its  life  period  the  rat  did  not  grow.  Calling  a  man's 
span  of  life  seventy  years  the  case  would  be  somewhat  like  that 
of  a  boy,  kept  as  a  healthy  infant  in  arms  until  fourteen  years 
old — -weighing  perhaps  sixteen  to  twenty  pounds — and  who,  by 
a  change  of  diet  when  fourteen  years  old,  attained  a  man's  size 
and  weight  at  the  age  of  twenty-one. 


THE   EFFECT  OF  FEEIiING   CORK  PROTEINS  ALONE 
OR   IK   COMBIHATIOH  WITH  MILK  OR  MEAT 


200 


nxys 

Chart  V. 

Two  of  the  rats,  5293  and  5316,  whose  curves  of  body  weight 
are  shown  in  Chart  V,  had  a  ration  in  which  the  protein  was 
furnished  by  gluten  feed.  Rats  5302,  5318,  5287  and  5315  on 
the  other  hand  had  two-thirds  of  their  protein  in  the  form  of 
gluten  feed  and  the  other  third  as  milk  or  meat.  The  nutritive 
ratios  of  all  of  these  three  foods  were  alike,  but  the  results  were 
strikingly  different. 

This  juggling  with  proteins  and  amino-acids  is  very  interest- 
ing to  the  chemist  and  physiologist  for  it  represents  a  triumph 
of  science  which  excites  the  wonder  of  those  who  appreciate  the 


THE  PROTEINS  OF  MILK. 


19 


almost  insurmountable  difficulties  encountered  in  these  investi- 
gations. It  would  be  of  little  use  to  discuss  it  here,  if  these  facts 
could  not  be  applied  to  the  feeding  problems  of  the  household 
and  farm.  Amino-acids  are  not  commercially  obtainable  but 
products  are  at  hand  which  contain  proteins  which  furnish  these 


'  -Sim 


Figure  4 

Figure  4  shows  photographs  of  some  of  the  animals  whose  curves  of 
body  weight  are  shown  in  Chart  V.  Although  all  three  were  of  the  same 
age,  Rat  5302  which  had  received  a  mixture  of  gluten  feed  and  milk  is 
nearly  three  times  as  large  as  5293  which  received  the  gluten  feed  alone 
and  more  than  four  times  as  large  as  5292  which  was  fed  on  zein  plus 
tryptophane. 


20  CONNECTICUT    EXPERIMENT   STATION    BULLETIN    215. 

amino-acids  in  readily  obtainable  form.     Now  let  us  see  how  we 
can  apply  these  facts. 

When  corn  as  a  whole  is  fed,  the  other  proteins  in  this  seed 
supplement  the  zein  to  such  an  extent  that  the  animal  can  grow 
slowly,  but  if  the  corn  is  combined  with  milk,  the  proteins  of 
which  are  rich  in  both  tryptophane  and  lycine,  growth  is  very 
rapid. 

Thus  it  appears  that  the  chemical  constitution  of  the  protein 
of  the  food  influences  growth  and  that  it  is  absolutely  necessary 
to  provide  animals  with  protein  of  the  right  kind,  if  they  are  to 
grow  well.  This  applies  not  only  to  growth,  but  also  to  milk 
or  egg  production.  Both  milk  and  eggs  are  rich  in  protein.  The 
animals  producing  them  need  large  amounts  of  protein  in  their 
food,  but  until  the  differences  in  the  chem'cal  constitution  of 
the  proteins  of  different  feeds  were  discovered,  it  was  not  appre- 
ciated how  important  it  is  to  provide  protein  of  the  right  kind. 
This  fact  has  been  unconsciously  recognized  by  milk  producers 
for  they  always  feed  protein  from  several  sources.  This  practice 
is  an  attempt  to  furnish  a  mixture  of  proteins  which  will  mutually 
supplement  each  other,  but  whether  the  mixtures  now  in  general 
use  are  yielding  the  best  results  at  the  least  cost  remains  to  be 
determined.  As  yet  we  do  not  know  the  actual  protein  require- 
ments of  milk  production.  Are  these  similar  to  those  of  growth? 
This  problem  remains  for  future  study. 

That  a  proper  combination  of  proteins  may  mean  much  in  the 
way  of  profits  when  growing  animals  are  fed  is  illustrated  by  the 
following  from  a  bulletin  recently  issued  by  the  Ohio  Agricul- 
tural Experiment  Station.  In  a  series  of  experiments,  compar- 
ing the  value  of  corn  alone  with  combinations  of  corn  and 
tankage,  or  corn  and  skim  milk,  it  was  shown  that  a  bushel  of 
corn  fed  alone  produced  only  nine  pounds  of  gain.  The  same 
quantity  of  corn  fed  in  combination  with  5.5  pounds  of  tankage 
produced  13.3  pounds  of  gain,  and  corn  fed  with  168  pounds 
of  skim  milk,  equal  to  17  pounds  of  dry  food,  increased  the  gain 
to  21.8  pounds  per  bushel  of  corn  fed.  In  other  words,  each  ten 
pounds  of  the  dry  matter  in  the  skim  milk  replaced  54.9  pounds 
of  corn.  Expressing  these  results  in  terms  of  dollars  and  cents, 
corn  alone  produced  pork  at  a  loss  of  $8.38  per  100  pounds  of 
gain,  whereas  nine  parts  of  corn  fed  with  one  part  of  tankage 
produced  pork  at  a  profit  of  $14.91  per  100  pounds  of  gain,  and 


THE  VITAMINES  OF  MILK.  21 

one  part  of  corn  fed  with  three  parts  of  skim  milk  yielded  a 
profit  of  $35.59  per  100  pounds  of  gain. 

The  Vitamines  of  Milk. 
Another  constituent  of  milk  which  has  a  unique  value  in  the 
dietary  is  the  butter  fat.  If  a  young  rat  is  fed  on  a  ration 
adequate  in  all  respects  except  that  the  fat  is  furnished  by  lard, 
or  vegetable  oils  like  olive  oil,  it  will  grow  normally  for  a  period 
of  about  80  days,  then  suddenly  it  declines  in  weight  and  soon 


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Chart  VI. 

Chart  VI  shows  that  butter  fat  contains  something  essential  for  normal 
growth.  These  curves  show  that  after  feeding  a  diet  of  purified  food- 
-  stuffs,  the  fat  being  lard,  the  animals  after  growing  normally  for  several 
weeks  suddenly  began  to  lose  weight.  When  a  part  of  the  lard  was 
replaced  by  butter  fat  (shown  by  the  beaded  line),  they  immediately 
recovered.  These  animals  would  have  died  in  a  few  days  if  this  change 
had  not  been  made. 


2  2  CONNECTICUT   EXPERIMENT    STATION    BULLETIN    21 5. 

dies.  Such  animals  frequently  suffer  from  sore  eyes  and  in  many 
cases  develop  large  ulcers  on  the  eyeball.  A  small  amount  of 
butter  fat  added  to  the  diet  causes  an  immediate  recovery  of 
health,  gain  in  weight  and  prompt  restoration  of  the  eyes  to  their 
normal  condition.  This  marvellous  effect  is  due  to  the  presence 
in  the  butter  fat  of  something  of,  as  yet,  unknown  nature,  which 
for  the  time  being  is  called  the  fat-soluble  vitamine.  The  presence 
or  absence  of  this  substance  in  any  foodstuff  can  be  detected  only 
by  feeding  young  animals. 

Chart  VI  shows  the  weight  curves  of  rats  which  declined  on  a 
diet  in  which  lard  was  the  sole  fat  component  and  then  rapidly 
recovered  when  part  of  the  lard  was  replaced  by  butter  fat. 

Recently  it  has  been  reported  from  some  parts  of  Europe  that 
many  children  have  been  afflicted  with  a  disease  called  xeroph- 
thalmia, which  is  characterized  by  the  development  of  ulcers  on 
the  eyeball. 

Figure  5  shows  a  photograph  of  a  child  thus  affected.  This 
condition  is  strikingly  like  that  exhibited  by  rats  fed  on  rations 
deficient  in  the  butter-fat  vitamine,  and  is  probably  due  to  the 
same  cause,  for  these  xerophthalmic  children  who  had  been  fed 
almost  entirely  on  skim  milk  and  cereals  were  promptly  cured 
by  whole  milk  or  cod  liver  oil.  It  is  still  unproved  that  this  butter 
fat  vitamine  is  essential  for  adults.  We  have  maintained  mature 
rats  for  many  months  in  good  condition  on  diets  containing  no 
known  source  of  this  substance,  and  as  yet  they  have  shown  no 
signs  of  malnutrition.  For  the  normal  growth  and  development 
of  the  young,  however,  it  is  absolutely  essential.* 

Just  what  these  vitamines  are  has  not  been  discovered  yet, 
but  at  least  three  types  exist,  namely  the  fat-soluble  or  "A" 
vitamine;  the  water-soluble,  "B,"  and  the  antiscorbutic,  "C" 
vitamine.      Milk    contains    some    of    the    antiscorbutic    vitamine 


*  It  is  worth  noting  that  Dr.  H.  C.  Wells,  who  had  charge  of  the  dis- 
tribution of  food  in  Rumania  for  the  American  Red  Cross,  tells  us  he  made 
successful  application  of  our  observation  that  cod  liver  oil  contains  much 
of  the  fat-soluble  vitamine. 

A  cargo  of  cod  liver  oil  at  Archangel  having  been  offered  to  him  he  im- 
mediately ordered  it  sent  to  Rumania  hoping  by  its  use  to  save  the  eye- 
sight of  thousands  of  children  whose  eyes  were  in  the  same  condition  as 
those  of  rats  fed  on  a  diet  deficient  in  the  fat-soluble  vitamine.  By  giving 
this  cod  liver  oil  to  these  children  a  large  majority  were  saved  from 
permanent  blindness,  even  after  their  eyeballs  had  become  entirely  opaque. 


THE  VITAMINES  OF  MILK. 


23 


which  prevents  scurvy,  though  less  than  do  some  of  the  vegetable 
and  fruit  juices,  notably  orange  juice.  This  vitamine  is  sensitive 
to  heat,  hence  children  fed  on  pasteurized  or  boiled  milk  are  more 
susceptible  to  infantile  scurvy  than  are  those  fed  on  unheated 
milk,  unless  the  scurvy-preventing  vitamine  is  given  them  in 
some  fruit  or  vegetable  juice  in  which  it  is  abundant. 

The  relation  of  the  fat-soluble  vitamine  to  nutrition,  and  its 
presence  in  butter  fat  have  already  been  discussed  at  considerable 


Figure  5 
This  child  was  fed  on  skim  milk,  and  as  a  result  an  ulcer  developed  on 
one  eyeball.  This  was  because  it  did  not  get  any  of  the  so-called  fat- 
soluble  vitamine  which  is  present  in  the  butter  fat.  Plenty  of  cream, 
butter,  or  cod  liver  oil  will  cure  this  child's  eye.  Young  rats  develop  this 
same  disease  when  fed  on  diets  free  from  the  fat-soIuMe  vitamine  and 
are  promptly  cured  by  adding  a  little  butter  to  their  diet.  (Photograph 
from  Bloch,  C.  E.,  Ugeskrift  for  Laeger,  Mar.  8,  1917,  79,  309,  349.) 


length.  It  is  only  necessary  to  add  that  this  vitamine  is  quite 
resistant  to  heat,  for  we  have  passed  live  steam  through  melted 
butter  fat  for  two  and  one-half  hours  without  destroying  its 
potency. 

The  third  type  of  vitamine,  known  as  the  water-soluble  vita- 
mine, is  also  present  in  milk.     Without  an  adequate  supply  of 


24  CONNECTICUT   EXPERIMENT    STATION    BULLETIN    215. 

this  food  accessory  in  the  diet,  life  cannot  be  maintained.  An 
animal  which  is  fed  on  a  ration  containing  no  known  source  of 
this  vitamine  dies  within  a  short  time.  If,  however,  when  ap- 
parently dying,  a  very  little  of  this  food  accessory  is  given,  it 
recovers  with  surprising  rapidity.  This  may  be  given  in  the  form 
of  milk,  yeast,  commercial  wheat  embryo,  or  any  other  natural 
foodstuffs. 


Days 

Chart  VII. 
Chart  VII  illustrates  the  typical  recovery  (in  Period  4)  of  a  rat  which 
had  declined  on  a  diet  lacking  the  so-called  water-soluble  vitamine 
(Periods  2  and  3),  when  the  animal  was  given  milk  which  contains  this 
vitamine.  This  rat  would  have  been  dead  in  a  few  days  if  the  milk  had 
not  been  given. 

Chart  VII  shows  the  rapid  decline  in  weight  typical  of  feed- 
ing a  food  deficient  in  the  water-soluble  vitamine.  It  also  shows 
the  effect  of  feeding  an  abundance  of  dried  milk  as  a  source  of 
this  vitamine. 

That  the  water-soluble  vitamine  is  something  apart  from  and 
independent  of  the  fat  or  protein  of  the  milk  is  shown  by  the 
results  of  our  experiments.  For  many  years  we  used  the  product 
obtained  by  evaporating  to  dryness  milk  freed  from  fat  and 
protein  as  a  source  of  the  water-soluble  vitamine  in  the  diets 
fed  to  our  experimental  animals. 


THE  VITAMINES  OF  MILK. 


25 


Chart  VIII ,  shows  that  this  product  which  we  have  called 
"protein-free  milk"  is  just  as  efficient  as  a  source  of  water- 
soluble  vitamine  as  is  the  whole  milk.  Contrary  to  what  appears 
to  be  generally  believed,  the  water-soluble  vitamine  is  resistant 
to  heat.  "Protein-free  milk"  prepared  by  evaporating  at  a 
temperature  not  far  below  that  of  boiling  water  is  just  as  efficient 


260 
24-0 
220 

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0  20  40  60  80  100  120  140  160  180  200  220  240  I 

Days 

Chart  VIII. 

Chart  VIII  Is  a  further  illustration  of  the  necessity  of  an  abundance  of 
the  water-soluble  vitamine  in  the  food,  if  the  animal  is  to  live.    In  Period 

1  the  animal  grew  normally  on  an  ordinary  mixed  diet.  In  Period  2, 
on  a  diet  adequate,  except  for  the  lack  of  this  vitamine,  it  declined  rapidly 
and  would  soon  have  died  if  some  source  of  this  vitamine  such  as  protein- 
free  milk  (milk  freed  from  fat  and  protein)  had  not  been  fed  (Period  3). 
The  protein-free  milk  contains  not  only  the  salts  and  the  lactose  of  the 
milk  but  also  the  water-soluble  vitamine.  On  the  casein  diet  the  weekly 
food  intake  (shown  by  the  dotted  line  at  the  bottom)  declined  steadily 
from  nearly  80  grams  to  a  little  over  20  grams,  but  rose  immediately  to 
about  80  grams  when  the  protein-free  milk  (water-soluble  vitamine)  was 
given. 


26  CONNECTICUT   EXPERIMENT    STATION    BULLETIN    215. 

as  a  source  of  vitamine  as  is  an  equivalent  quantity  of  fresh, 
unheated  milk.  Even  boiling  for  several  hours  does  not  destroy 
this  vitamine. 

By  what  means  this  vitamine  exerts  its  marvellously  beneficial 
influence  is  still  unknown.  The  rapid  gains  in  weight  following 
its  use  are  always  accompanied  by  a  very  great  increase  in  the 


Figure  6. 

The  lower  picture  shows  a  rat  which  had  been  fed  for  one  month  on  a 
diet  deficient  in  water-soluble  vitamine.  At  this  time  the  animal  was  so 
weak  it  was  scarcely  able  to  stand  and  would  have  died  in  a  few  hours  if 
some  source  of  this  vitamine  had  not  been  furnished.  After  the  picture 
was  taken  a  small  daily  dose  of  yeast  which  is  very  rich  in  the  water- 
soluble  vitamine  was  given  to  the  rat,  the  food  remaining  otherwise 
exactly  as  before.  Twelve  days  later  the  upper  picture  was  taken.  The 
result  is  apparent. 

amount  of  food  eaten,  the  weekly  food  intake  frequently  being 
doubled  and  sometimes  even  quadrupled  when  a  small  amount  of 
vitamine-containing  food  is  given  to  an  animal  declining  on  a  food 
free  from  water-soluble  vitamine.  The  vitamine  may  act  simply 
as  a  stimulant  to  a  jaded  appetite,  and  the  better  growth  may  be 


THE  VITAMINES  OF  MILK.  27 

due  solely  to  the  increased  food  intake;  or  it  may  supply  one 
or  more  essential  factors  needed  to  complete  an  inadequate  diet, 
and  the  effect  of  adding  the  vitamine  may  be  analogous  to  that 
obtained  by  adding  a  missing  amino-acid,  or  a  sufficient  supply 
of  some  inorganic  element  which  was  present  in  too  small  an 
amount  to  permit  of  normal  nutrition.  When  we  know  more 
about  the  chemical  nature  of  the  vitamines,  we  may  be  able  to 
discover  just  what  part  they  take  in  the  processes  of  nutrition. 

Professor  Hopkins  of  England  reported  some  experiments  in 
which  he  obtained  very  striking  results  by  feeding  daily  small 
quantities  of  fresh  milk  to  rats  which  were  on  a  diet  supposedly 
free  from  water-soluble  vitamine.  From  his  data  the  conclusion 
was  drawn  that  milk  is  very  rich  in  this  type  of  food  accessory. 
In  some  recent  attempts  to  duplicate  his  results,  we  found  it 
necessary  to  use  much  larger  quantities  of  milk  than  he  did  in 
order  to  get  comparable  results. 

Undiluted  milk  contains  all  the  vitamine  necessary  for  the 
young  animal,  but  in  feeding  babies  it  is  the  practice  to  dilute 
cow's  milk  with  water  and  to  reinforce  the  mixture  with  milk 
sugar.  By  this  procedure  the  vitamine  content  of  the  original 
milk  is  so  far  reduced  that  the  bottle-fed  baby  may  get  enough 
of  this  essential  food  factor  only  when  it  takes  a  liberal  quantity 
of  the  food.  Whenever  appetite  fails,  the  food  intake  and  conse- 
quently the  vitamine  intafke  are  reduced.  The  effect  of  this  is 
to  further  reduce  the  appetite  because  the  amount  of  food  eaten 
depends  on  the  vitamine  content  of  the  diet.  It  is  thus  evident 
that  under  such  circumstances  the  child  goes  from  bad  to  worse 
and  the  endless  troubles  so  familiar  to  mothers  ensue.* 

In  feeding  young  animals  trouble  is  rarely  encountered  when 


*  In  this  connection  it  is  interesting  that  Dr.  Amy  L.  Daniels  and  Dr. 
Albert  H.  Byfield  have  just  published  in  the  American  Journal  of  Diseases 
of  Children  a  report  of  their  experience  with  additions  of  the  water- 
soluble  vitamine  to  the  milk  diets  of  bottle-fed  babes.  These  experiments 
were  founded  on  our  discovery  that  milk  contains  less  water-soluble  vita- 
mine than  had  been  previously  supposed.  In  each  case  there  was  a  marked 
increase  in  the  rate  of  growth  of  the  infant  when  the  additional  vitamine 
was  given  and  a  slowing  of  the  rate  when  it  was  omitted.  From  these 
experiments  it  appears  that  the  standard  milk  mixtures,  used  for  feeding 
infants,  furnish  too  little  of  the  water-soluble  vitamine  even  when  con- 
sumed in  normal  amounts. 


28  CONNECTICUT   EXPERIMENT    STATION   BULLETIN    21 5. 

the  food  is  right.     On  the  other  hand  very  sHght  defects  in  the 
food  lead  to  countless  difficulties. 

The  Sugar  of  Milk. 
At  present  we  do  not  know  whether  or  not  milk  sugar  has 
any  greater  value  for  nutrition  than  have  other  carbohydrates.  It 
has  been  thought  that  liberal  quantities  of  milk  sugar  in  the  diet 
produce  lactic  acid  in  the  intestine  and  thus  transform  the  bac- 
terial flora  from  a  type  which  produces  putrefaction  to  one 
which  checks  this  process.  None  of  the  other  kinds  of  carbo- 
hydrates tested  has  this  effect,  but  to  what  extent  this  change  is 
advantageous  to  the  body  is  as  yet  undecided. 

The  Mineral  Matters  of  Milk. 
Milk  also  holds  a  valuable  place  in  the  average  dietary,  on 
account  of  the  composition  of  its  mineral  constituents.  Cereal 
foods  contain  relatively  little  calcium,  sodium  or  chlorine,  hence 
animals  are  unable  to  grow  on  diets  composed  solely  of  cereals 
unless  these  inorganic  deficiencies  are  supplemented.  Milk,  on 
the  other  hand,  is  rich  in  calcium,  for  it  contains  about  three 
times  as  much  as  does  the  entire  wheat  grain,  and  about  six  times 
as  much  as  does  corn  meal.  The  presence  of  an  abundant  supply 
of  calcium  in  the  food  is  essential,  for  it  not  only  contributes  to 
the  maintenance  of  the  proper  neutrality  of  the  body  fluids,  but 
is  needed  to  form  strong  and  well-developed  skeletons.  A  liberal 
consumption  of  milk  by  growing  children  is,  therefore,  desirable 
as  a  "factor  of  safety"  against  deficiencies  in  the  mineral 
nutrients  of  the  other  constituents  of  the  dietary. 

The  Cost  and  Economy  of  Milk. 

Now  let  us  consider  the  cost  of  this  exceptionally  valuable 
food  as  compared  with  other  common  foods  and  see  how  much 
truth  there  is  in  the  statement  that  its  cost  makes  its  free  use 
prohibitive  to  all  but  a  few. 

It  is  difficult  to  put  an  exact  value  on  a  complicated  product 
like  milk,  but  a  fair  estimate  of  its  relative  value  compared  with 
other  food  products  can  be  reached  by  calculating  the  cost  of  the 
several  types  of  food  elements  in  milk  and  other  staple  products. 
Milk  suffar  has  the  same  food  value  as  cane  sugar.     We  can 


COST  AND  ECONOMY  OF  MILK  '  29 

buy  a  pound  of  the  latter  for  11  cents,  so  we  may  assign  this 
vakie  to  the  sugar  in  milk.  Milk  fat  has  a  higher  value  than  have 
ordinary  food  fats  as  shown  by  the  higher  price  of  butter,  but 
let  us  assume  that  in  milk,  fat  is  worth  no  more  than  lard,  say 
about  35  cents  a  pound. 

One  hundred  pounds  of  average  milk  contain  about  12.5  pounds 
of  solids  of  which  five  pounds  is  sugar,  worth  55  cents  at  11 
cents  a  pound,  and  four  pounds  of  fat  worth  $1.40  at  35  cents 
a  pound,  or  $1.95  for  the  fat  and  sugar.  One  hundred  pounds 
of  milk  contain  46^  quarts,  which  at  16  cents  a  quart  is  $7.45. 
Subtracting  $1.95  from  $7.45  leaves  $5.50  for  the  3.3  pounds  of 
dry  protein  in  the  one  hundred  pounds  of  milk,  or  $1.67  per 
pound. 

Now,  how  much  does  dry  protein  cost  in  meat  or  eggs?  One 
hundred  pounds  of  lean  round  of  beef  contain  7.3  pounds  of 
fat  worth  $2.55.  Subtracting  this  from  $50,  which  one  hundred 
pounds  of  this  cut  of  beef  now  costs  at  retail,  leaves  $47.45  for 
19.5  pounds  of  dry  protein,  or  $2.43  a  pound;  76  cents  a  pound 
more  than  milk  protein.  The  difference  is  even  greater  for  eggs, 
for  by  the  same  method  of  calculating,  in  storage  eggs  at  55  cents 
a  dozen  protein  costs  $2.64  a  pound,  or  97  cents  a  pound  more 
than  milk  protein.  According  to  this  method  of  calculation  only 
when  the  lean  round  of  beef  sells  for  35  cents  a  pound  and  eggs 
sell  for  35  cents  a  dozen  are  they  as  cheap  sources  of  protein  as  is 
milk  at  16  cents  a  quart.  Thirty-five  cents  spent  for  milk  at  the 
present  price  buys  nearly  as  much  protein,  about  two  and  one- 
half  times  as  much  fat  and  more  than  twice  as  much  energy  as 
is  contained  in  a  pound  of  lean  Hamburg  steak.  In  buying  milk, 
moreover,  one  is  procuring  protein  of  exceptional  value  because 
it  enhances  the  nutritive  value  of  our  cereal  foods.  In  addition 
one  is  obtaining  a  liberal  supply  of  vitamines,  whose  value  cannot 
be  estimated  in  dollars  and  cents,  for  as  yet  we  have  no  adequate 
knowledge  regarding  their  relative  abundance  in  different  foods. 

Since  milk  is  so  vitally  essential  as  a  food  for  growing  chil- 
dren and  is  such  a  valuable  supplement  to  a  diet  composed  largely 
of  cereals,  vegetables,  meat,  sugar  and  fats,  the  production  of 
milk  should  be  stimulated  so  that  there  may  be  an  abundance 
of  milk  and  milk  products  of  the  highest  possible  grade  at  prices 
which  shall  put  them  within  the  reach  of  all. 


30        connecticut  experiment  station  bulletin  215. 

Summary. 

Milk  is  absolutely  essential  for  the  life  of  infants  and  very 
young  children. 

It  is  a  most  desirable  adjunct  to  the  diet  of  older,  rapidly 
growing  children. 

It  is  the  main  dietary  reliance  in  cases  of  disordered  digestion 
or  extreme  illness. 

Milk  contains  an  abundance  of  protein,  fat,  carbohydrate  and 
mineral  nutrients,  and  its  proteins  are  not  only  of  superior  value 
when  used  alone,  but  they  are  especially  adapted  to  supplement 
the  protein  deficiencies  of  the  cereals  which  form  so  large  a  part 
of  the  daily  ration  of  mankind.  Its  mineral  nutrients  also 
supplement  the  deficiencies  of  the  cereals,  meat,  sugar  and  fats 
in  these  important  elements.  Moreover  it  contains  the  three 
vitamines  without  which  life  cannot  be  maintained. 

The  scurvy-preventing  vitamine  is  destroyed  by  heat  and  there- 
fore if  infants  are  fed  on  pasteurized  or  sterilized  milk  the  use 
of  orange  juice  or  some  vegetable  extract  is  necessary  to  avoid 
the  possibility  of  scurvy. 

Whole  milk  contains  enough  water-soluble  vitamine  to  meet 
an  infant's  requirements,  but  if  "the  top  of  the  bottle"  diluted 
with  water  is  fed,  the  supply  of  this  essential  vitamine  may  be 
insufficient  unless  it  is  supplemented  from  some  other  source. 

Milk  is  the  only  food  known  which  is  capable  of  serving  as 
the  sole  constituent  of  an  adequate  ration. 

Milk  is  a  cheaper  form  of  food  at  i6  cents  a  quart  than  either 
beef  at  35  cents  a  pound  or  eggs  at  35  cents  a  dozen. 


3n 


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